1. Technical Field
The present invention relates to a method for manufacturing a flexible printed circuit board and, particularly, to a method for manufacturing a multilayer flexible printed circuit board having different thicknesses in different areas.
2. Discussion of Related Art
Hollowed printed circuit boards are printed circuit boards that are hollowed. Two sides of the hollowed area are exposed to exterior thus the hollowed printed circuit board can provide electrical connection on the two sides.
A method for manufacturing such a hollowed printed circuit board includes steps of: laminating a first dielectric layer having an opening preformed thereon on a first surface of a copper layer; forming conductive patterns in the copper layer; and laminating a second dielectric layer having an opening preformed thereon on a second surface of the copper layer, the two openings are aligned with each other thereby defining a hollowed area in the conductive layer.
Usually, a protective layer is used to protect the first surface of the copper layer when the conductive patterns are formed. However, there is a cliff-like structure between the first dielectric layer and the conductive layer, creating gaps between the protective layer and the conductive layer. Thus, etchant can infiltrate into the gap to damage the conductive layer.
Therefore, there is a desire to develop a method for manufacturing a hollowed printed circuit board that prevents damages in the conductive layer.